This model has a 106-nucleotide insertion in the leptin receptor gene causing premature termination of the intracellular region of the leptin receptor, leading to an inhibition of leptin signaling in the hypothalamus and unchecked hyperphagia, obesity, hyperinsulinemia, and increased leptin levels [67,71,72]. Here, LEP is linked to obesity due to melanocortin 4 receptor deficiency.